Air rifle is impractical in such situations (you'll do more damage to the house with anything that's on the legal limit than you'll do to the mouse). If the bed smells then mouse boy (or girl) has probably being peeing in it for a while. You'll want to get rid sooner rather than later if that's the case. Either put traps down (but for the love of god not in a location you'll get your toes (or anything else) caught in the middle of the night or call the exterminators in. Just hope they don't come up with something as wonderful as they did with my parents 'oh that's a rare breed of wasp we can't do anything to them they're protected'. Tell that to the people/animals they've stung before we called you genius!
As for the cat idea it's not bad but if the cat can't get into the roof and indeed that's where they are then it's pointless, even if the cat can get into the roof you have to get it back down. Also you run the risk that the cat's not that way inclined or leaves bits of mouse to stink the place out again in a location you can't get to.